Depolyalkylation process for producing para-t-butyl toluene



United States Patent DEPOLYALKYLATION PROCESS FOR PRODUC- IN G PARA-t-BUTYL TOLUENE No Drawing. Application October 14, 1955 Serial No. 540,611

3 Claims. (Cl. 260--671) This invention relates vto the preparation of t-butylated aromatic hydrocarbons by reaction of a polyisobutylene and a hereinafter defined aromatic hydrocarbon.

It is normal to produce t-butyl aromatic hydrocarbons such as t-butyltoluene by the direct alkylation of toluene or other aromatic hydrocarbon with isobutylene. The production of an essentially pure t-butyltoluene requires the use of very high purity isobutylene, which olefin is an expensive item of commerce.

It has been known that diisobutylene can be used with certain acid catalysts to produce t-butylated aromatic hydrocarbons such as t-butyltoluene. However, with the catalyst taught in the art, this depolyalkylation process for the production of t-butylated aromatic hydrocarbons is inefiicient because of low yields, high catalyst consumption and numerous side reactions. Such a depolyalkylation process is of considerable commercial interest because polyisobutylenes, such as diisobutylene and triisobutylene are very readily obtained in high purity at relatively cheap cost.

An object of the invention is a process for the preparation of t-butylated aromatic hydrocarbons such as t-butyltoluene. Another object is a process for utilizing polyisobutylene as a source of iso-C groups for the preparation of t-butylated aromatic hydrocarbons. Still another object is a depolyalkylation process utilizing polyisobutylene for the preparation of substantially pure para-t-butyltoluene in very high yield. Yet another object is a depolyalkylation process utilizing alkylatable benzene hydrocarbons and a polyisobutylene, which process utilizes a relatively cheap catalyst having a long catalyst life. Other objects will become apparent in the course of the detailed description.

Briefly, the process involves a depolyalkylation reaction of one or a mixture of the aromatic hydrocarbons, benzene, alkylbenzene, dialkylbenzene and trialkylbenzene, wherein the alkyl group contains from 1 to 4 carbon atoms, these aromatic hydrocarbons being capable of accepting a t-butyl substituent, with either diisobutylene, triisobutylene, or tetraisobutylene to obtain a t-butylated aromatic hydrocarbon product. The aromatic hydrocarbon may contain more than one type of alkyl group; the preferred alkyl groups are methyl and ethyl. The reaction is carried out in the presence of a BF -hydrate type catalyst which contains from about 66 to 80 weight percent of BF The reaction is carried out at a temperature between about 0 C. and 120 C.

The aromatic hydrocarbon chargedto the process must be alkylatable by at least one iso-C, group. The iso-C group is defined herein as one which will produce a t-butyl substituent. Suitable aromatic hydrocarbons are benzene, methyl or ethylbenzene, dimethyl or diethylbenzene, or ethylmethylbenzene, 1,2,3-trimethyl or triethylbenzene or a mixture of these alkyl groups. The invention is particularly suitable for the preparation of mono-t-butylated aromatic hydrocarbons such as mono-t-butylbenzene and t-butyltoluene. By proper adjustment of the catalyst, time, and temperature, it is possible to obtain a t-butylated monoalkylbenzene which is substantially entirely para oriented, for example, para-t-butyltoluene.

The olefin charged to the process is a polyisobutylene containing from 2 to 4 iso-C groups. The iso-C group may be considered as the equivalent of an isobutylene molecule for the purposes of alkylation. Thus diisobutylene contains 2 iso-C, groups and tetraisobutylene contains 4 iso-C, groups. Because it is very readily available in extremely high purity and appears to depolymerize somewhat more readily, it is preferred to utilize diisobutylene.

It is desired to produce an alkylate which is principally the mono-t-butylated aromatic hydrocarbon. In order to attain this object, the mole ratio of alkylatable hydrocarbon charged and the polyisobutylene is adjusted so that at least about 1 mole of aromatic hydrocarbon is present for each iso-C group present. To illustrate: When charging toluene and diisobutylene, at least about 2 moles of toluene are present for each mole of diisobutylene. When charging triisobutylene, at least about 3 moles of toluene would be present per mole of triiso butylene. The presence of more aromatic hydrocarbon is helpful in maximizing the yield of the mono-t-butylated product. In general, as much as 3 moles of aromatic hydrocarbon per mole of iso-C, groups or even more may be present in the reaction zone. It is preferred to operate with about 1.5 moles of aromatic hydrocarbon per mole of iso-C group. To illustrate: When utilizing toluene and diisobutylene, the preferred mole ratio of toluene to diisobutylene is about 3.

The catalyst utilized in the depolyalkylation process of the invention is a BF -hydrate type. The catalyst may consist essentially of BF and water in the desired ratios. Or, the catalyst may contain hydrocarbonaceous materials dissolved therein from previous use as a catalyst in the depolyalkylation reaction. The amount of BF present in the catalyst is between about 66 and weight percent. When utilizing essentially only BF and water, the mole ratio of BF to water corresponds to about that of the monohydrate, i.e., a mole ratio of 1. Operation with the lower concentrations of BF tends to produce lower yields of alkylate based on aromatic hydrocarbon charged. Operation with the higher concentrations of BF, produces excellent yields of alkylate, but the t-butylated alkylbenzenes tend to be high in meta oriented materials. When it is desired to produce substantially only the para oriented t-butylalkylbenzene, it is preferred to utilize a catalyst containing from about 69 to 72 weight percent of BF At least a catalytically effective amount of the catalyst must be present in the reaction zone. Some depolyalkylation reaction will occur with even very small amounts of catalyst which might be described as that amount which exceeds solubility of the catalyst in the hydrocarbons. In general, the volume ratio of total hydrocarbon charge to the reaction zone to the catalyst will be from about 1 to 15. It is to be understood that smaller ratios and larger ratios may be used. It is preferred to operate with a volume ratio from about 5 to 9. The term total hydrocarbons charged is intended to include the aromatic hydrocarbons plus the polyisobutylene charged to the reaction zone.

In order to obtain appreciable amounts of the t-butyl aromatic hydrocarbon product, it is necessary to operate at a temperature of at least about 0 C. At lower temperatures, direct alkylation plays an important part and octyl aromatics are produced when utilizing diisobutylene. At temperatures above about C., cracking reactions come into play and it is more ditlicult to obtain high purity t-butyl aromatic hydrocarbons in good yields. At the very low temperatures, time does play a part in the production of high yields of the t-butylated aromatic hydrocarbons. At room temperature and higher, time plays a smaller role and is of real importance only when it is desired to produce t-butylalkylbenzene, which is substantially only the para isomer. When operating at C., the reaction may go for as long as 12 hours; at 120 C. or at other elevated temperatures, the depolyalkylation reaction may be essentially complete in as little as one minute.

When it is desired to produce t-butylalkylbenzene, substantially entirely the para isomer, i.e., on the order of 80 mole percent or more para isomer in the t-butylalkylbenzene product fraction, it is preferred to operate at a temperature between about 20 C. and 50 C. Prolonged times increase the amount of meta isomer present in the product and, therefore, the time is controlled at these temperatures for between about 5 minutes and 30 minutes; in general, the higher the temperature the lower the corre sponding time.

The results obtainable with the process are illustrated by several working examples set out below. These working examples involve the use of benzene, toluene, orthoxylene and meta-xylene as aromatic hydrocarbons and diisobutylene and triisobutylene as the iso-C, group donors. The techniques utilized are described in detail in conneo tion with Run 1.

RUN 1 In this run and all the other runs, the aromatic hydrocarbons were nitration grade and the polyisobutylenes were technical grade. The mole ratio of toluene or benzene or xylene to diisobutylene in all the runs was 2. The

total hydrocarbon to catalyst volume ratio utilized in the runs was 7.

The runs were carried out utilizing either fresh catalyst which had never been used before in any reaction,

.or used catalyst, which catalyst had been used at least once in a depolyalkylation reaction. The fresh catalyst was prepared utilizing commercial anhydrous boron trifluoride anddistilled water. Typically, a known amount of distilled water was placed in a 4 liter flask equipped with a gas dispersion tube and a Dry Ice cooled condenser.

The flask was placed in an ice bath and the BF bubbled into the water until no more was absorbed. The rate of BF addition was controlled to keep the temperature of the liquid in the flask below C. When no more B1 was absorbed, the calculated composition, based on BF added was 78.2 weight percent BF and the remainder water. This solution, when analyzed for BF content by conventional procedures, gave a BF weight percent of 76.5. Herein, all BF -hydrate type catalyst compositions are given as weight percent of BF found on analysis.

A typical run utilizing toluene as the aromatic hydrocarbon and diisobutylene as the olefin is set out in detail.

Seven moles (644 gms.) of toluene and 190 ml. of BF .H O were charged to the reactor. Three and onehalf moles of diisobutylene (403 gms.) were charged to the dropping funnel. The stirrer was started and water was circulated through the condenser atop the reactor. The diisobutylene was then added dropwise (approx. 25 mL/min.) to the reacting system. The temperature rose from 23 to 36 C. in about two minutes. At this point ice water was circulated through the reactor coils until the temperature dropped to 33 C., then the circulation was stopped. A reaction temperature of 33 to 36 C. was maintained by this method. At the end of 23 minutes all the olefin had been added, after which the stirring was continued for approximately one minute. After the stirrer was stopped, the reaction mixture separated into two layers. The hydrocarbon layer was drawn off into a separatory funnel with a small amount of hydrocarbon being left on the catalyst layer to prevent BF loss'to the atmosphere. The hydrocarbon layer was washed with 200 ml. distilled water, then with 200 ml. of 10% KOH and finally washed again with 200 ml. of distilled water. The product was then dried overnight with 150 gms, of calcium chloride.

The product was distilled on a 70-plate hypercal column using a 10:1 reflux ratio. The cuts from hypercal with infrared spectrometer analyses are shown below.

The t-butyltoluene produced was blended into a high octane number refinery gasoline base to produce a blend containing 25 volume percent of the t-butyltoluene. The octane number of the blend was determined by the F-1 method (CPR-Research) and the blending octaine number of the t-butyltoluene determined. In a base having an F-l number of 94.6, the t-butyltoluene had a blending octane number of 114. This compares with an octane number, under these circumstances, of 111 for toluene and 109 for a mixture of C aromatic hydrocarbons derived from catalytic reformate. These octane data show that t-butyltoluene is an excellent high octaine component of gasoline; an additional very desirable feature is the fact that it is sufliciently high boiling to improve the octane number of the tail end of the gasoline which is frequently deficient in high octane components.

The very high purity para-t-butyltoluene obtainable by the process of the invention is an excellent raw material for the manufacture of para-t-butylbenzoic acid, which material is in considerable demand at this time as a chemical intermediate.

RUNS 2-5 Several runs were made on the preparation of t-butyltoluene from toluene and diisobutylene in order to note the efiect of contacting time on the product distribution. In all of these runs, fresh catalyst analyzing 76.5 weight percent of BF;, was used. All the runs were carried out in the temperature range of 32-37 C. The results of these runs are set out in Table A below.

Table A Run No 2 3 4 Reaction Time (M'inutesl 300 32 7 Yiel'ls (Mol Percent on Toluene Reacting):

t-bltyltol'iene 77. 9 82. 0 35. 9 84. 9 3,5-di-t-h'1tyltoluene 7. 8 4. 7 5. 5 3. 0 Toluene Reacting 93. 0 88. 3 88. 5 85. 0

The data show that when utilizing this particular catalyst at this temperature the depolyalkylation reaction proceeds very rapidly. There is some indication that extremely long contacting time at this temperature has a beneficial effect on the total amount of toluene reacting. However, this extremely long time has the bad effect of increasing the yield of the di-t-butyltoluene at the expense of yieldof t-butyltoluene.

RUNS 6-11 butyltoluene yield remained about the same at the expense 1 isomer andafter min No. 10, in excess of 90% of the .t-butyltoluene product fraction is the para isomer.

Other conclusions to be drawn from the data present in Table C are that at constant temperature, as the age to the isomeric distribution of the t-butyltoluene. The tests show that at use 6, not reported, over 80% of the t-butyltoluene product was the para isomer. As the catalyst aged, the distribution shifts markedly to the para of di-t-butyltoluene production. With fresh catalyst it 5 of the catalyst increases, time has more bearing on the appears that the lower temperatures are definitelydesiryield and product distributlon. At a given contacting able with respect to maintaining a very high proportion of time, as the catalyst ages, higher temperatures are nectolue reacting, essary to obtain very high yields.

RUN 12 A second study of catalyst age was made maintaining The eflect of catalyst age was studied in this run. Most the F i temperature .about 33460 and a of the tests were carried out at about room temperature f i g a g g g i E fi g i for a time of about 300 minutes. Some tests were made e 1 a o a 0 es p mug e under different conditions. Although a total of indiylelds excess 60% of charged vidual tests were carried out in this run No. 12, only 8 were obtamefi Wm} h t'butlilmluelF Welds based representative tests are set out in Table C following. The 15 zgg g i g il 80 Atduse g and reaction conditions, product distribution and particularly if d1 7 f 1; g o E mac very isomer distribution used and obtained at various catalyst :22? e i on t f 'f ages (number of uses) are set out in Table C. appears a ca a ys can e a east Table B Run No 6 7 8 9 10 11 Reaction Temperature t C.) 0'5 33-36 -48 57-60 69-72 100-110 Yields (M01 Percent on Toluene Reacting):

t'butyltolueue 82.0 86.5 76.7 84.3 85.8 84.5 3.5di-t-butyltoluene 0.8 5.1 4.9 4.8 6.1 1.2 Toluene Reacting 86.4 87.5 85.6 86.5 86.1 77.4

Product Distribution (Wt. Percent of Total Product):

IBP250 F. (Toluene 0110-- 8.9 9.4 10.5 10.5 10.2 14.6 250-305 F 0.4 0.5 0.4 0.4 0.6 0.6 ass-400 F. (t-butyltolncne 0110.- 74.9 76.1 66.0 72.6 75.1 69.0 400 F.+ (3,5-di-t-butylt0luene and diisobutylene polymers) 15.8 14.0 23.1 16.5 14.1 158 Table C Catalyst Age (Uses) 1 4 7 9 11 12 14 15 Reaction Temperature C.) 33-36 18-28 23-30 31-86 510 36-38 31-35 34-36 Reaction Time (Minutes) 300 300 330 360 300 270 480 300 Yie ds (M01 Percent on Toluene Reacting) t-Butylto .ene 77.9 82.7 89.8 91.3 81.2 93.8 90.3 89.0 3.5-dit1Bntyltoluene... 7.8 5.1 1.0 1.2 None 0.5 0.3 None Toluene Reacting 93.0 99.1 97.0 97.8 85.5 99.0 98.0 82.0 Isomer Distribution (Wt. Percent):

para-t-Butylt0luene 54 74 85 .84 92 92 91 98 meta-t-Butyltoluene.-. 46 26 15 16 8 8 9 7' The data presented in Table 0 show that at least 24 times. On this basis, about 10 gallons of alkylate can through 15 Successive uses the catalyst is effective in probe produced per pound of BF}; consumed; this is based on ducing very high yields of t-butyltoluene. Examination the assumption that the catalyst will not be regenerated,

of the data show that as the catalyst ages the yield of although the catalyst can be recovered at some cost. di-t-butyltoluene decreases until at the eleventh use the yield of the di-t-butyltoluene was essentially zero. Of RUNS 13-16 very great interest are the results of the tests with respect In these runs, diisobutylene was reacted with meta- Xylene, ortho-xylene and benzene. An attempt was made to react with phenol. The results of these runs are set out in Table D.

1 N 0 reaction.

The data show that with benzene as the aromatic hydrocarbon, very litt1e di-t-butylbenzene was produced. About 80% of this was the para isomer. In the case of ortho-xylene, essentially all the product was the 1,2-dimethyl-4-t-butyibenzene showing that under these conditions little or no isomerization takes place.

RUNS 17-18 Table E Run Number 17 18 Wt. Percent BF, in BIG-H20 Catalyst 76. 0 70.1 Reaction Temperature C.) 14-38 -33 Reaction Time (Minutes) 54 64 Toluene/Triisobutylone (M01) 3/1 3/1 HydrocarbonlCatalyst (Vol.) 7/1 7/1 Yields (Moi Percent on Toluene R 3.5-di-t-Butyltoluene 4. 1 None Toluene Reacting 1 85. 2 '13 Triisobutylene Reacting 99+ Isomer Distribution (Wt Percent) p-t-Butyltoluene 62 92 Toluene Aocounted For (Moi Percent) I l 85 98 Triisobutylene Accounted For (M01 Percent) 1 73 87 -8 Reaction temperature C.) 75-80 Reaction time (min utes) 127 Toluene/tripropylene (molar) 1.5/1 Hydrocarbon/ catalyst -(volume) 7 1 Toluene reacting 70.0

v Yields (mol percent on toluene reacting):

lsopropyl toluene 1.0 t-Butyltoluene 5.5 Amyltoluene 14.0

Total depolyalkylate 20.5

Higher boiling aromatics (assumed to be nonyl" toluene) 51.4

The data set out in the illustrative examples show clearly that by the use of the defined BF -hydrate type catalyst, under the defined conditions of time and temperature, a process'results wherein the defined aromatic hydrocarbons can be converted in very high yield to t-butylated aromatic hydrocarbons. Furthermore, the

" t-butylalkylbenzene products can be made to be substantially'entirely the para isomer and can, by a suitable adjustment of time, temperature and catalyst age, be obtained as a fraction containing in excess of 90% of the para isomer.

1 Remainder of toluene and triisobutylene believed to be in bottoms fraction as heavy polymer and octyl (or higher alkyl) toluene.

In this run, it was attempted to depolyalkylate toluene using tripropylene as the olefin. The results of this run show that tripropylene under these conditions does not depolymerize;'instead, cracking occurs as well as alkylation with the tripropylene itself. The results of this run are set out in the following table.

Thus having described the invention what is claimed is:

1. A process for'the preparation of t-butyltoluene containing substantially only the para-isomer, which process comprises depolyalkylating toluene with diisobutylene, in a mole ratio of toluene to iso-C; groups in said diisobutylene of between about 1 and 3, in the presence of a BF -hydrate catalyst containing between about 69 and 72 weight percent of Bf the volume ratio of said toluene plus said diisobutylene to said catalyst being from about 1 to 15; at a temperature between about 20 C. and C. for a time between about 5 and 30 minutes, separating catalyst from a hydrocarbon product mixture and recovering from said mixture a t-butyltoluene product fraction containing in excess of of p-t-butyltoluene.

2. The process of claim 1 wherein said mole ratio is about 1.5.

3. The process of claim 1 wherein said volumeratio is between about 5 and 9.

References Cited in the file of this patent UNITED STATES PATENTS 2,376,119 Bruner May 15, 1945 2,436,110 Larsen Feb. 17,1948 2,836,634 Lee et al. May 27, 1958 

1. A PROCESS FOR THE PREPARATION OF BUTYLTOLUENE CONTAINING SUBSTANTIALLY ONLY THE PARA-ISOMER, WHICH PROCESS COMPRISES DEPOLYALKYLATING TOLUENE WITH DIISOBUTYLENE, IN A MOLE RATIO OF TOLUENE TO ISO-C4 GROUPS IN SAID DIISOBUTYLENE OF BETWEEN ABOUT 1 TO 3, IN THE PRESENCE OF A D-5 HYDRATE CATALYST CONTAINING BETWEEN ABOUT 69 AND 72 WEIGHT PERCENT OF BF3, THE VOLUME RATIO OF SAID TOLUENE PLUS SAID DIISOBUTYLENE TO SAID CATALYST BEING FROM ABOUT 1 TO 15, AT A TEMPERATURE BETWEEN ABOUT 20*C. TO 50* C. FOR A TIME BETWEEN ABOUT 5 AND 30 MINUTES, SEPARATING CATALYST FROM A HYDROCARBON PRODUCT MIXTURE AND RECOVERING FROM SAID MIXTURE A T-BUTYLTOLUENE PRODUCT FRACTION CONTAINING IN EXCESS OF 80% OF P-T-BUTYLTOLUENE. 